it's means when object insert new records it's id set null so don't need to create again. if you only set it to "NULL" Magento will only think you don't want to update the value.
– Magento2 DevloperAug 23 '17 at 19:31

It worked! Just one question: I've been told before to never load models in a loop because it kills performance, that would be just for the method load? E.g: $product = Mage::getModel('catalog/product')->load($item->getProductId()); Is it okay to instantiate a model in a loop?
– StordonAug 23 '17 at 19:08

Prince, do you mind helping me with some other way, then? This worked fine, but if there is a better and faster way, I'd like to see it, for performance is one of my priorities
– StordonAug 23 '17 at 19:19